ABS Warning Light

The ABS (Anti-lock Braking System) warning light indicates a fault in your car's ABS system. When illuminated, it means the system may not function correctly during emergency braking, potentially increasing stopping distances. Common causes include a faulty wheel speed sensor, low brake fluid, or a blown fuse. While the car's standard brakes will still work, you should get it checked by a professional as soon as possible to restore full braking safety.

If the ABS light comes on, follow these steps:

1. Check the brake fluid level and top it up if necessary.
2. Inspect the fuse box for any blown fuses related to the ABS system.
3. Look for obvious damage to wheel speed sensors or their wiring.
4. If the light stays on after these checks, visit a garage for diagnostics.

Modern cars like the Ford Focus or Vauxhall Corsa use complex ABS systems that require specialist diagnostic tools to pinpoint issues. Ignoring the warning could lead to reduced braking performance, especially in wet or icy conditions where ABS prevents wheel lock-up. The repair cost varies - a sensor replacement might cost £100-£200, while an ABS module repair could exceed £500.

The Anti-lock Braking System (ABS) is an active safety feature in vehicles, commonly referred to as the ABS braking system. It is an improvement over conventional braking systems. The ABS mainly consists of an ECU control unit, wheel speed sensors, brake pressure modulation devices, and brake control circuits.

How the Anti-lock Braking System works:

During braking, the ABS control unit continuously receives speed signals from the wheel speed sensors, processes them, and determines whether a wheel is about to lock up. The characteristic of ABS braking is that when a wheel approaches the lock-up threshold, the brake caliper pressure does not increase with the master cylinder pressure; instead, the pressure fluctuates near the lock-up threshold.

If the wheel does not enter a lock-up state, the brake pressure modulation device does not engage, and the braking force continues to increase. If the ECU detects a tendency for a wheel to lock up, it sends a command to the brake pressure modulation device to close the channel between the brake cylinder and the wheel cylinder, preventing further increase in wheel pressure.

Reasons for the ABS light to illuminate:

1. When the vehicle speed exceeds 10 km/h, no speed signal is transmitted to the ABS control unit;
2. When the vehicle speed exceeds 40 km/h, the speed signal deviates beyond the tolerance range;
3. The sensor has a detectable open circuit or a short circuit to the positive terminal or ground.

Solutions for the ABS light illuminating:

1. Carefully inspect the wiring and connectors for poor contact or damage;
2. Check the installation gap and position of the wheel speed sensor and the tone ring, as well as contamination by dust or debris;
3. Inspect whether the wheel bearing clearance is too large and adjust it to the normal value;
4. Avoid high-speed driving and sudden braking, and take the vehicle to a 4S shop for inspection as soon as possible.

From a mechanic's perspective, an illuminated ABS light typically means one of three things: a sensor issue (most common), hydraulic problems, or control module faults. Wheel speed sensors often fail due to road debris or corrosion. A quick diagnostic scan can identify which wheel is affected. While drivable, the car won't have anti-lock braking functionality, so drive cautiously, especially in poor weather.